Certain operations in the manufacture of textile products require a metering device for supplying a predetermined length of material to the needle of the machine. In many instances, it is desirable to feed an elastic material to the needle under an elasticized state. One patented invention related to elastic metering devices, is disclosed in U.S. Pat. No. 2,901,991 granted on Sept. 1, 1969 to G. M. Reimer. In this patent there is disclosed an elastic metering device for a sewing machine in which the elastic is fed through a pair of feed rollers which serve to measure and place under tension the elastic strip prior to feeding same to the needle. Of the two feed rollers disclosed in the above mentioned patent, one is connected via a rock lever to the needle drive mechanism of the machine. The driven feed roller has contained therein a clutch roller for driving the feed roller upon one direction of movement of the lever. There is also contained within the feed roller a stationary shaft which is provided with cam formations thereon so as to coact with the clutch rollers in preventing rotation of the feed roller in a direction opposite to that in which the feed rollers are initially driven but allowing a freedom of movement of the rock lever to its initial position.
As will be made more apparent hereinafter, the Reimer structure is distinguished from the present invention by the provision that all of the driving motion in the patented invention is delivered to the driven feed roller upon the downward movement of the lever. The Reimer patent also has a drawback in that a plurality of parts are contained within the feed roller and thus inaccessible.
By way of contrast, the present invention discloses means for imparting movement to the metering device upon both directions of movement of the rock lever so as to provide a more uniform speed for the feed roller. More particularly, the present invention includes a plurality of feed rollers which are supportably carried on the upper arm of the machine. As disclosed in the Reimer patent, there are suitable connections between the needle drive and the rock lever so as to oscillate the latter. This rockable or oscillatable lever is connected to a first one way clutch assembly means which is operably associated with one of said feed rollers for imparting movement thereto. The driven feed roller further carries a second one way clutch assembly which further aids in imparting motion to the feed roller during the opposite movement of said oscillatable lever. A motion transfer mechanism interconnects the clutch assemblies and provides for cooperative operation, that is, opposite movement in unison such that any oscillatory movement of the rock lever will result in a feeding displacement of the metering device. The motion transfer means includes a plurality of levers, one of which is pivotally secured to the support member so as to reverse the direction of movement between the first and second clutch assemblies. A brake assembly which includes a friction block totally encompassing a portion of the outside diameter of the driven feed roller together with an adjustable resilient member combine to apply a braking force against said shaft, thus serving to prevent overthrow of the driven feed roller in the course of its operation.
As stated above, with the patented invention all of the driving movement for the roller is delivered during the downward stroke of the rock lever. This meant all of the elastic that was to be used during that stitch had to be delivered in the downward stroke, thus the curvilinear velocity of the roller had to be sufficient to perform the same. Whereas by providing a mechanism wherein movement is imparted during both directions of the rock lever, an extended period of time for supplying the same extent of material is provided. That is, by driving the roller during both lever directions a slower curvilinear speed is required thus less overthrow of the mechanism results. Due to the slower roller speed, and thus lower inertia force of the roller, a lesser extent of braking force is required to be placed on the driven roller. Another advantage by the provision of a drive working in two directions is that the braking force is applied to the feed roller in a symetrical manner. Whereas, in the Reimer patent, the braking force is not effective upon the advance of the feed roller but effective upon its return movement which results in an uneven braking effect and thus a variable force is delivered to the needle drive mechanism of the machine.
As may be apparent, the provision of the present invention has numerous advantages over the art, and has for a primary object, to provide a simple and compact means for delivering a predetermined length of material to the stitch forming area during operation of the machine.
Related to the foregoing, the present invention has for a further object the provision of the metering device having a considerably reduced inertia force value.
It is yet another object of this invention to provide means which have the same curvilinear output for only one half of the linear input as has been heretofore required.
It is a further object of this invention to provide means for providing a symetrical braking pressure on the feed roller throughout the feeding cycle.
In the accompanying drawings annexed hereto and forming part of this specification, the present invention is shown embodied as an elastic metering device associated with a sewing machine, but it will be understood that some of the features of this invention can be embodied in other devices that the drawings are not to be construed as defining or limiting the scope of the invention, the claims appended to this specification being relied upon for that purpose.